When to Change Spark Plugs?

[bigmck]

I have a 2004 4.0L with 56,000 miles. I have never had the spark plugs changed. Is there a mileage level where they should be changed? Will changing them help gas mileage? Thanks,

 

[1AJeremyD]

Welcome to the forum! The mileage that most dealers recommend is 100K on spark plugs. If you replace them earlier, you probably won't notice any significant difference in your gas mileage. If you do a complete tune up with air filter spark plugs and wires fuel filter and run a can of sea foam through the truck you might notice a better difference but it is up to your budget and what you're up to doing.

 

[matt0248]

Personaly I don't like leaving plugs in the head for 100k miles. I changed my 4.6L plugs at 5 yrs @ 50k. I will do it again at 100k.

 

[edwx]

I agree with matt...time to change 'em. 6+ years is long enough. Suggest Autolite XP's, or Motorcraft. The Autolites worked really well in my '03 XLS.

 

[imp]

WTH is "sea foam"????: imp

 

[Hawkeye61]

Seafoam is an additive you can add to your engine oil or to your fuel. They also make other products. I use to be a auto parts store manager and most all the mechanics around here love the stuff.

 

[Blrob]

I would say every 30,000 miles, especially if you bought the truck used and don't know if they have been changed at all.